Control of fuel burners



May 16, 1961 D. A. MONK 2,984,297

CONTROL OF FUEL BURNERS Filed March 30, 1959 INVENTOR DEN/.5 AUBREY Mame I 7 ATTORNEY Unite 1 States CONTROL OF FUEL BURNERS Filed Mar. 30, 1959, Ser. No. 802,684

2 Claims. (Cl. 158-28) This invention relates to apparatus for effecting the automatic control of multi-fuel burners, particularly in multi-burner installations, and has for its main object to provide means for improving the degree of selective control of such burners when using flame detection devices of known form.

In equipment of this character, it is usual to provide each fuel burner with its own flame detector and in many cases its own ignitor, which may or may not have a separate flame detector, and in cases where only one flame detector is provided, the main flame detector will also receive signals from the ignitor flame and handle these in a proper sequence. Most furnaces are provided with more than one burner and the invention is therefore particularly applicable to multi-burner installations which may be regarded as installations comprising a number of burner and flame detection units, each selfcontained from the point of view of automatic sequence but at the same time each burner and flame detection unit being open to outside influences, such as the cross indication between neighbouring burners and flame detectors.

The detection of a particular flame in a furnace fitted with more than one fuel burner has always suffered from the lack of discrimination, on the part of the flame detcetor, between the burner flame being monitored and any other flame in the same furnace, and the normal result of this lack of discrimination between neighbouring sets of fuel burners and their associated flame detectors is the indication of the presence of a flame in a particular burner where in fact the opposite is the case, which will create a hazardous stiuation.

Although the standard flame detector possesses a wide degree of sensitivity, full use is seldom made of this quality due to the usual practice of fitting flame detectors in such a manner that any one flame detector is able to view more than one burner flame, and owing to the methods of fitting the flame detectors in multi-burner installations usually employed, lack of discrimination invariably occurs due to the positioning of the various components.

The present invention accordingly consists in an apparatus for effecting the automatic control of fuel burners in multi-burner installations wherein reflector means are provided inside the burner casing which are adapted to cooperate with a flame detector in such a Way as to enable such detector to view the root of the burner flame against a target wall and thereby enable the flame detector to sight the individual burner flame to the exclusion of any other flame in the same furnace.

According to the preferred arrangement, the aforesaid reflector means comprises a quartz prism in an adjustable container fitted as an integral pressure tight unit to a sighting tube and target area in one direction and to a flame detector fitted to a carrier tube in another direction.

The invention will be more completely understood from the following detailed description which is given in conjunction with the accompanying drawing in which:

2,984,297 Patented May 16, 1961 Fig. 1 is a sectional side view of a fuel burner in which a flame detector constructed in accordance with the invention is embodied; and i Fig. 2 is an enlarged detail showing the construction of the flame detector.

Referring now to this drawing, the burner is constructed of tubular form, the walls 1 terminating in a burner throat tile ring 2 and surrounding the oil burner 3, the coal burner 5 or the gas burner 4, the burner tile ring 2 being secured to the furnace plate 6 so as to form a throat projecting into the furnace, and the central tube 3 being slidably mounted for longitudinal movement in a guide tube 7, and terminating at its rear end in an oil gun of any suitable known type, not shown.

The composite flame detector assembly consists of a number of main sections, which comprise firstly a quartz prism 8 for the purpose of receiving and reflecting flame radiation from the particular burner to which it is associated, to the exclusion of any other burner; to direct this radiation to the flame detector 9 at a desired and convenient point on the burner or furnace casing 10; secondly a prism box 11 constructed fro-m stainless or heat resisting steel designed to hold the prism in a predetermined position with suitable fittings to ensure that the prism will remain in a fixed position during service and will be replaced accurately upon re-assembly; thirdly, a radial tube 12, constructed from stainless or heat resisting steel, designed to limit and to maintain the predetermined angle of vision; fourthly a special arrangement of one of the burner throat tiles of the tile ring 2 having a recessed part 13 to accommodate the selected position of the prism box 11 and a radial passage 14 to accommodate the radial tube 12; and further a special arrangement of a tile 2a of the tile ring 2 directly opposite the position of the radial tube 12 so that the line of sight from the flame eye 9 through the prism 8 will view the root of the flame against a black spot target area 15; and lastly the flame detector sighting tube 16 holding the flame detector 9 at the outer end and provided with suitable fittings 17 at the inner or furnace end to ensure correct alignment between the standard commercial flame detector 9 and the rest of the components. The sighting tube 16 is conveniently constructed from stainless or heat resisting steel and is preferably provided with diaphragms and/ or some form of serrated or non-reflecting surface inside to reduce the angle of vision and eliminate reflections.

The arrangement for a flame detector operating exclusively on the ignitor flame would be similar to the above description for liquid fuel but might not need a prism for gaseous fuel.

Apart from ensuring that the proper line of sight is maintained through the train of components, there are certain other requirements to be met regarding the assembly of the various items comprising the complete prismatic flame detector.

Normally the size, length, position and form of all components are predetermined and preset but latitude is available in the design of the various components to meet the particular requirements of individual installations. The axis of the flame detector will normally be set at to the final line of sight across the burner throat and the root of the flame although this angle may be modified to suit surrounding constructional details. The optical system between and including the flame detector, the sighting tube, the prism box, the prism and the radial tube will be pressure tight to prevent ingress of dirt and other extraneous matter and suitable adjustable fittings are included to give this requirement on final assembly. The final line of sight between the prism and the burner flame is deep set in the burner throat away from the furnace proper, parallel to the furnace wall, normal to the burner axis.

What is claimed is 1. In a furnace having a burner wall provided with athroat opening and having a burner disposed to fire through said throat opening, a throat tile ring disposed in said opening, said tile ring having therein a radial passage extending at right angles to the axis of the burner and adapted to receive light rays emitted by the flame from said burner and means defining a dark target spot disposed on said tile ring diametrically opposite and in alignment with said radial passage, a sighting tube extending parallel to the axis of said burner and having its rearward end disposed in said wall and in communication with said radial passage, reflector means disposed at the intersection of said sighting tube and said radial along said sighting tube and a light sensitive device carried by said tube in registration with the path of said light rays for sensing the presence of a flame in said burner throat.

2. The combination set forth in claim 1 in which said 5 reflecting means comprises a quartz prism.

References Cited in the file of this patent UNITED STATES PATENTS 10 2,295,045 Mettler Sept. 8, 1942 2,404,903 Cohen July 30, 1946 2,598,808 Ledin June 3, 1952 2,797,336 Loft June 25, 1957 OTHER REFERENCES Fuel Oil and Oil Heat, March issue, 1951, page 85.

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